Guides

Plain-English guides to the math you actually use, from percentages and quadratics to statistics and geometry. Each guide walks through the idea step by step with worked examples.

Step-by-step guides

The guides here answer the practical questions that come up in projects around the home and shop. They cover how much material to buy, such as gravel, paint, and fence posts, how to work out sizes, such as roof pitch, wire size, and deck footings, and how fasteners and bolt grades differ, along with plain-English glossaries of building terms.

Each guide walks through the idea in steps and uses worked examples, so you can follow the reasoning and then repeat it with your own measurements. Most link to a calculator that does the arithmetic for you, which makes it easy to check your own work and try different numbers.

The guides give general information for planning. Codes, local conditions, and product specifications vary, so confirm anything structural, electrical, or safety related with your local building department or a qualified professional before you begin.

Getting the most from the guides

Read a guide from the top the first time, since each builds on the idea before it. When you are ready to calculate, take your own measurements, note the units, and check the result against the worked example. If your answer is far from what you expected, recheck the measurements before you trust the number or buy material.